1. Field of Invention
The present invention relates to an antenna structure. More particularly, the present invention relates to an antenna structure on a circuit board for dual band operation.
2. Description of Related Art
The communication technology has been well developed and plays an important role in the daily life. Particularly, the wireless telecommunication is an important way to communicate with a person in moving terminal. For example, the cellular phone is very popular now in wireless communication. Antenna in wireless communication is the necessary element to transmit and receive the radio frequency (RF) signal.
Antenna implemented into the communication device for transmitting or receiving RF signals by various ways. However, in order to have adapt into the communication device in a compact way, antenna can be directly form on a substrate, such as a printed circuit board, which can directly connect to the electronic circuit of the transceiver. Also and, in order to have the more choice to communicate, the electronic circuit is designed to be able to operate in dual-band mode. In this manner, the antenna should also be able to be operated in dual-band mode. The dual-band operation occurs quite often. For example, the cellular phone at different area is operated in different frequency band. However, the same antenna is used in these two frequency bands.
Since the structure of the antenna will determine the response efficiency for the specific frequency band, the antenna structure is still under designed to be adapted into various communication device. For the manufacturers, how to design the proper antenna, particularly to the cellular phone, is still in development. The easy structure with acceptable performance is more strongly desired when the dimension of the communication device is further reduced.